[19] G. E. Herberich, E. Bauer, J. Hengesbach, U. Kolle, G. Huttner, H. cyclopentadienide l[3b1reacted with C,H; and solvated Lorenz, Chem. Ber. 1977, ff0, 760. nickel(@ bromide to give the nickelocene 2 (two pairs of [20] 7: Monoclinic, space group P2Jn (No. 14) with u = 12.406(4), b = enantiomers syn-2alb and anti-Za/b in the ratio 5: l).15]De- 6.733(2), c = 16.390(4) A, = 95.11(2)", V = 1363.6(5)A3, and 2 = 4 (e.,.,, =1.685 gcm-'), p(MoK.) = 93.18 cm-', 3997 unique reflections, protonation of 2 yielded the green anion 3,15] a key com- 3777 with F, 2 0.6u(F) were used in refinement; R = 0.0466, pound for further reaction with transition metal ions. The R, = 0.0452; GOF = 1.22. Further details of the crystal structure investi- title compound 4C51 was obtained after addition of solvated gation are available on request from the Director of the Cambridge Crys- tallographic Data Centre, University Chemical Laboratory, Lensfield chromium(i1) chloride to a solution of 3 in THE 4 is an Road, GB-Cambridge CB2lEW (UK), on quoting the full journal citation. air-sensitive compound isolated as mossy green crystals of [21] a) G. E. Herberich, W. Boveleth, B. Hessner, D. P. J. Koffer, M. Negele, R. 4 . toluene from toluene and solvent-free olive-green glitter- Saive, 1 Organomel. Chem. 1986,308, 153; b) W. Siebert, M. Bochmann, ing platelets from hexane (42 % yield). J. Edwin, C. Kriiger, Y-H. H. Tsay, Z.Nururforsch. B1978,33,1410; c) G. Huttner, W. Gartzke, Chem. Ber. 1974. 107,3786; d) G. E. Herberich, B. Hessner, S. Beswetherick, J. A. K. Howard, P. Woodward, J. Orgunomet. Chem. 1980,192,421; e) G. E. Herberich, B. Hessner, M. Negele, J. A. K. / I Howard, J. Orgunomet. Chem. 1987, 336, 29.

/-Hf Stepwise Stacking of Three I Paramagnetic Metallocene Units: [CpNiCp(SiMq), CpCrCp(SiMe,), CpNiCp]* * By Pierre Bergerat, Janet Blumel, Monika Fritz, Johann Hiermeier, Peter Hudeczek, Olivier Kahn, Cr C12 and Frank H. Kohler* I Molecular materials which are ferro-, ferri, or antiferro- magnetic as a result of interactions between spin-carrying metal centers are currently subjects of intensive research.['' A particularly rich chemistry is derived from chelate com- pounds in which like and-more promisingly-unlike metals are assembled in close proximity.["I Other spin sources are organometallic compounds. Thus, the reactions of poly- The cyclic voltammogram of 4 (Fig. 1) shows five electron alkylmetallocenes with tetracyanoethylene and related elec- transfers leading to a pentacation. An interaction between tron acceptors yield the salts [CpZM]' [K anion]- which the two terminal nickelocenes is disclosed by splittings of 65 crystallize as stacks and exhibit spontaneous magnetization and 190 mVf61associated with the potentials for the oxida- at low temperature when the metal is iron, manganese, or tion to the nickelocene monocations (near 1 V) and dications chromium.['] In these materials the stacks are linear, that is, (near 2 V), respectively. Not surprisingly for highly charged vertical with respect to the plane of the K ligands, and' their stability is determined by ionic interactions. This organometalEc/organic concept implies that different metal centers cannot be introduced in one stack by using simple sandwich molecules. We wished to explore an alternative concept concerning pure organometallic compounds with stacking orientations other than vertical, with covalent bonding between the metallocenes, and with two different paramagnetic metal centers. We therefore synthesized biscyclopentadienyl lig- ands that may serve to link different metallocenes in a stereo- chemically well-defined manner.[31After testing less reactive diamagnetic synthetic building blocks and their complexa- /. 0 0.5 1.0 1.5 2.0 2.5 tion behavior14]we report here on the title compound 4, the EIVl prototype of a heteronuclear compound containing three - paramagnetic metallocene units. Fig. 1. Cyclic voltammogram of 4 in propionitrile, 8 x molL- ', -2O"C, The synthesis (Scheme 1) is based on the stepwise metala- scan rate 200 mVs-', potential E vs internal Cp,Co/Cp,Co+. Electron trans- fers from left to right: El,, (AE,) 340(65), 980(80), 1045(80), 1850(170), tion of two doubly bridged cyclopentadiene~.[~]Thus the 2040(105) mV; assignment see text.

[*I Prof. Dr. F. H. Kohler, Dr. J. Bliimel, Dr. M. Fritz, Dr. J. Hiermeier, DipLChem. P. Hudeczek Anorganisch-chemisches Institut der Technischen Universitat Miinchen species, the electron transfers leading to the tetra- and penta- Lichtenbergstrasse 4, D-W-8046 Garching (FRG) cation are chemically not reversible. The central chromocene Prof. 0.Kahn,'*' P. Bergerat is oxidized more easily (J!?,,~= 340 mV) in accord with what Universite de Paris Sud is known from the parent metall~cenes.['~In addition, a Laboratoire de Chimie Inorganique, CNRS URA 420 broad, unresolved wave with E, = - 1140 mV indicates the F-91405Orsay (France) irreversible reduction to 43 ['I Wilhelm Manchot Research Professor of the Technische Universitat -. Miinchen 1991. From the paramagnetic compound 4 we have obtained [**I This work was supported by the Pinguin-Stiftung, the Deutsche 13C NMR signals in the range from 6 = - 400 to + 1600 Forschungsgemeinschaft, and the Fonds der Chemischen Industrie. (Fig. 2). Their number and their approximate areas are in

1258 0 VCH Verlagsgesellschuft mbH. W-6940 Weinheim, 1992 0570-0833/Y2/090Y-1258$3.50+ .25/0 Angew. Chem. In[. Ed. Engl. 1992, 3f, No. 9 both contributions are operative. These contributions are not correlated below 50 K, although they are correlated above 50 K, so that the fitting of the magnetic susceptibility xMualong the direction u by Equation (a)["] is expected to

I600 1400 200 0 -200 -6 provide a reliable value of J. Since both DNiand D,, con- tribute to the zero-field splitting within the magnetic pair Fig. 2. I3C NMR spectrum of 4 in [DJTHF at 298 K; the two sections have state they cannot be determined separately. We therefore different vertical scales. S = solvent, Cp' = C1-3, C3a, and C8a. assumed that D,, is negligible with respect to DNi.With somewhat idealized the fitting yielded a Zeeman factor of g = 1.98, a zero-field splitting of agreement with the structure shown in Scheme while DNi= 28.7 cm-' (both are close to the values for nickel- their shifts are characteristic of substituted nickelocenes ocene itself['41), and the Ni"-Cr" interaction parameter (weighted average 6 = 1400 to 1500[91) and chromocenes J= -1.95cm-'; the agreement factor'"] was R = (weighted average 6 x - 300 to -400[91). It follows that, at 3.8 x The corresponding theoretical curve is given in ambient temperature, 4 has six unpaired electrons with each Figure 3. Considering that D,, is not negligible leads to the metallocene unit accommodating two of them. This is con- same energy spectrum for the low-lying states with a differ- firmed by the 'H NMR spectr~rn.~~]Surprisingly, however, ent value for DNibut the same for J. the signals of HI-3 at 6 = - 221.6 are shifted about 10% The magnetic properties are the crucial proof that the silyl less than the Cp protons of mononuclear nickelo~enes.[~~ bridges in 4 function as "valves" that allow a limited elec- Since it was not clear whether this points to spin exchange tron-exchange interaction. In this particular case it is anti- between the metallocenes, we performed solid-state magnet- ferromagnetic. Other metal combinations and the manipu- ic measurements. lation of the silyl bridges are conceivable so that the mag- The magnetic behavior is illustrated by the plot of xMTvs T (Fig. 3). At 250 K, xMT is equal to 2.94 cm3Kmol-', netism of trinuclear metallocenes should be adjustable. which corresponds to what is expected for three uncoupled The properties of the title compound 4 illustrate that the approach discussed at the beginning, the stepwise stacking of ions with SNi,= SNi,= S,, and is in agreement metallocene units, actually works. Compound 4 is a good with the NMR results. When the temperature is lowered, x,T decreases more and more rapidly and reaches model for analogous polymers, since here structure, redox 0.83 cm3Krnol-' at 1.9 K. Such behavior may arise from the behavior, and interactions between the metallocene units, in particular magnetic exchange, may be investigated conve- niently.

Received: January 23, 1992 [Z 51441Ej German version: Angew. Chem. 1992, 104, 3285 3'5 i CAS Registry numbers : 1, 142947-25-9; syn-2, 142947-26-0; anti-2, 142947-29-3; 3, 142947-27-1 ; 4, I 3l 142947-28-2; Cp-, 12127-83-2; NiBr,, 13462-88-9; CuCI,, 10049-05-5.

a) J. S. Miller, A. J. Epstein, W. M. Reiff, Chem. Rev. 1988, 88, 201-220; b) A. Caneschi, D. Gatteschi, R. Sessoli, Arc. Cheni. Re.7. 1989, 22, 392- 398;c) 0. Kahn, Phil. Trans. R. Soc. Lond. A 1990,330,195-204; d) A. L. Buchachenko, Russ. Chern. Rev. Engl. Trunsl. 1990, 59, 307-319. a) J. S. Miller, J. C. Calabrese, A. J. Epstein, R. W Bigelow, J. H. Zhang, W. M. Reiff, J. Chem. Soc. Chem. Commun. 1986, 1026-1028; b) J. S.

I Miller, J. C. Calabrese, H. Rommelmann, S. R. Cbittipeddi, J. H. Zhang, 2345 I W.M. Reiff, A. J. Epstein, J. Am. Chem. SOC.1987,109,769-781 ; c) W E. Broderick, J. A. Thompson, E. P. Day, B. M. Hoffman, 1990,249, I I I I I I 1 Science 0.5 401-403; d) W. E. Broderick, B. M. Hoffman, J. Am. Chem. Soc. 1991, 0 50 100 150 200 250 ff3, 6334-6335; e)G.T. Yee, J. M. Manriquez, D. A. Dixon, R. S. TIKl - McLean, D. M. Groski, R. B. Flippen, K. S. Narayan, A. J. Epstein, J. S. Miller, Adv. Muter. 1991, 3, 309-311. Fig. 3. Magnetic properties of 4 represented as a plot of xD,TvsTwith xM being a) H. Atzkern, F. H. Kohler, R. Muller, Z. Nuturforsch. B. 1990,45,329- the molar magnetic susceptibility and T the absolute temperature. A: Experi- 343; b) J. Hiermeier, F. H. Kohler, G. Miiller, OrganornetaNics 1991, 10, mental values, solid line: calculated curve. Inset: expansion of the low-temper- 1787- 1793; ligand 1has been synthesized independently: U. Siemeling, R. ature range. Krallmann, P. Jutzi, Abstr. IXth Int. Conf. Silicon Chem. Edinburgh, 1990; U.Siemeling, P. Jutzi, Chem. Ber. 1992. f25,31-35; U. Siemeling, P. Jutzi, B. Neumann, H.G. Stammler, M. B. Hursthouse, OrgunometaNics 1992, ff. 1328-1333. local anisotropies DNiand D,, of the metal@) ions, and the [4] M. Fritz, J. Hiermeier, N. Hertkorn, F. H. Kohler, G. Miiller. G. Reber, 0. isotropic intramolecular magnetic interaction J between the Steigelmann, Chem. Ber. 1991, 124,1531-1539, In principle, the synthetic central Cr" and the terminal Ni" ions. Based on the pertinent steps described for iron correspond to those used here for nickel. spin Hamiltoniant"I the respective role of the two contribu- [5] The isomer ratio of syn-2alb to anti-2alb was determined by 'HNMR spectroscopy. syn-2alb: I3C NMR (THF, 310 K): 6 = 6551597 (Ca/6), tions becomes evident from the plot of xMT vs T when -15.1/56.6 (Cg/y). 114.6 (C2), 139.2/132.2 (C1/3); 29Si NMR (THF, T approaches zero: neglecting J would result in 319 K): 6 = - 845/- 873 (Si4/8). unti-2alb: I3C NMR (THF, 310 K): zMT> 1.3 cm3 K mol-I ; neglecting DNiand Dcr would result S = 220/519 (Cct/S), 85.7/98.4 (Cpiy), 191.8 (C2), 140.6/127.9 (C1/3); 29Si in a plateau with T 1 cm3 K mol-I. The latter corre- NMR (THF, 319 K): 6 = - 832/- 852 (Si4/8). The signal-to-noise ratio xM = did not allow the localization of the broad Cp carbon signals expected at sponds to the temperature range in which only the triplet 6("C) > 1000 similar as for 4 (Fig. 2). syn/anti-2a/b gave a satisfactory ground state is thermally populated. It turns out (Fig. 3) that elemental analysis. EI-MS (70 eV): rnjz (rel. intensity) 366 (Mt, loo), 351

Angew. Chem. Int. Ed. Engl. 1992, 31, No. 9 0 VCH Verlugsgesellschaff mbH. W-6940 Weinheim, 1992 0570-0833/92/0909-1259$3.50+ .25/0 1259 (M' - CH,, 4), 300 (M' - C5H6,2), 285 (Mt - CH3 - C,H,, 3), 183 2-(Dimethylaminomethyl)ferrocenyllithium (1) served as (M2+,3); the M+signal shows the theoretically expected isotope pattern. the starting material, which is readily accessible by metala- - 3: I3C NMR (THE 298 K): 6 = 1600 (Cp, C5-7, C4a/7a), 511/34 (Ca- 6), 135.7 (C3a/8a), 125.6 (C2), 100.1 (C1/3); 29Si NMR (THF, 298 K): tion of (dimethylaminomethyl)ferrocene"6' with n-butyl- 6 = - 842. 4: 'H NMR ([DJtoluene, 303 K) 6 = - 239.6 (Cp), - 221.6 lithi~m.['~1In THF solution 1 rapidly reacts with elemental (H1-3), 224.0 (H5/7), 163.0 (H6), 0.610.3 (Ha-6); 29Si NMR (THF, sulfur, selenium, or tellurium under insertion of a chalcogen 305 K): 6 = 313; EI-MS (70eV): m/z (rel. intensity) 784 (M', loo), 660 (M' -CPNi, 7) and small unassigned peaks; the M+ signal shows the atom into the lithium4arbon bond. The crystalline lithium theoretically expected isotope pattern. A satisfactory elemental analysis chalcogenolates 2-4 can be isolated in high yield from the was obtained for 4. toluene. resulting solution. The yellow-brown solids are readily sol- [6] The poorly resolved splitting near 1 V was estimated as described in: H. uble in THF, but almost insoluble in diethyl ether and hydro- Atzkern. J. Hiermeier, F. H. Kohler, A. Steck, J. Orgunornet. Chem. 1991, carbon solvents. 408, 281 -296. [7] a) N. G. Connelly, W. E. Geiger, Adv. Orgunornet. Chern. 1984, 23, 1-93; b)V. V. Strelets, Russ. Chern. Rev. Engl. Transl. 1989, 58, 297-311. [S] The study of the tris-iron analogues excludes the all-cis arrangement [6]. [9] F. H. Kohler, W. A. Geike, .l 0rganornet.Chem. 1987, 328, 35-37 and earlier contributions in the series. Note that we have changed the sign convention since. [lo] Calculated from xuT = (NB2/3k) (4gi, + 2g:J where g,; and g,, are the local Zeeman factors and the other symbols have their usual meaning. 1 2, E = S (73%) [I11 H =- J (s~i+ SN,d Sc. + SN,IDNi SN~,+ SN~,DNi SNi2 + Sc, Dc, 3, E = Se (84%) S,, + p(SN,,+ SNiJ g,, + S,, ' g,, ' H, where DN and 0,. are the local anisotropy tensors and gNiand g,, are the local Zeeman tensors. 4, E = Te (100%) [12] In Equation (a) the summation runs over the 27 levels E,," in the presence of the magnetic field H,. The powder magnetic susceptibility was calculat- ed by averaging over 15 directions of the magnetic field. The energies Ei." were obtained by diagonalizing the spin Hamiltonian of ref. [Ill using the Red-brown single crystals of the composition [Li(dme)J- I Ms(Nil),M,(Cr), M,(Ni2) > functions as a basis set. Then the parameters [CpFe{C,H,(CH,NMe,)Te}] were obtained by recrys- J, D,,, and g were determined by minimizing the agreement factor tallization of 4 from dimethoxyethane (DME). In contrast to = x[(xMT)caI - (~MT).bs12/~[(~MT)Ob'12~ other alkali metal tellurolates, which are very sensitive to 1131 DNiand the zero-field splitting parameter DNj(= 30,,,,/2) were assumed oxidation, crystalline [Li(dme)][CpFe(C,H,(CH,NMe,)Te}] to he axial, and gNiand gc, to he isotropic with the same principal g value. [14] P. Baltzer, A. Furrer, J. Hullinger, A. Stebler, Inorg. Chern. 1988, 27, can be handled in air for a short period of time without 1543-1548 and references therein. noticeable decomposition. The X-ray structure analysis['*] reveals that the Li-Te unit is stabilized by intramolecular chelate formation (Fig. I). The six-membered chelate ring

Chelate Stabilization of a Monomeric 9 Lithium Tellurolate** By Heinz Gornitzka, Susanne Besser, Regine Herbst-Irmer, Uirike Kilimann, and Frank T Edelmann* Metal complexes with alkoxide (RO-) and thiolate lig- ands (RS-) have been well studied." 31 However, only a few with selenolate and tellurolate ligands (RSe- and RTe-, respectively) are kn~wn.[~-~]They are of interest as precur- sors for metal chalcogenide~,~~~~~and also play an ever in- Tel creasing role as reagents in organic synthe~is.[~-~~~-"]In both cases alkali metal chalcogenolates act as intermediates. Fig. 1. Crystal structure of [Li(dmej][CpFe{C,H,(CH,NMe,)Te}]. Selected Sodium tellurolates are for example accessible by the reduc- bond distances [pm] and angles ["I: Tel-Lil 273.4(4), Lil-N1 207.9(4), N1-CI1 147.8(3), Cll-C2 149.0(3), C2-Cl 144.0(3), Cl-Tel 212.2(2), Lil-01 195.3(5), tion of the corresponding ditellurides with sodium amalgam Lil-02 201.0(4), Cl-Fel 206.3(2), C2-Fel 203.9(2); C1-Tel-Lil 74.2(1), Tel- or sodium in liquid ammonia.['21 They can undergo reac- Lil-N1 103.7(2), Lil-N1-Cl1 111.0(2), N1-CI1-C2 111.2(2), C11-C2-Cl tions to give transition metal teIIuroIates[' 3l as well as 124.5(2), Cll-C2-C3 127.1(2), C2-Cl-Tel 125.5(2), C5-Cl-Tel 127.9(1), C2- compounds with Te-C bond^.[^-"^ Very little is known Cl-CS 106.6(2), Tel-C1-Fel 128.1(1j, Cll-C2-Fel 126.6(2). about the structural chemistry of alkali metal tellur- olates: only [Li(thf),][2,4,6-rB~~C~H,Te]"~]as well as [Na(tmeda)][2,4,6-Me3C,H,Te] and [K([18]crown-6)][2,4,6- adopts a slightly distorted boat conformation, in which Te 1, iPr3C,H,Te]"51 have been structurally characterized. In all C1, C2, and C 11 are found almost in a plane. Noteworthy three cases bulky substituents led to a kinetic stabilization of is the relatively small angle at the tellurium atom (74.2(1)"). the alkali metal tellurolate. We have now found that the The Te-C bond length (212.2(2) pm) lies in the normal range. stability of alkali metal chalcogenolates can also be increased Their easy accessibility and unusual stability render the dramatically by chelation. Crystalline lithium chalcogeno- lithium chalcogenolates 2-4 of interest for subsequent reac- lates are readily accessible also in the case of the higher tions. Air oxidation of THF solutions leads to the corre- sponding dichalcogenides [{CpFe[C,H3(CH2NMe2)E]}21 homologues by incorporation of a Li-E unit (E = S, Se, Te) into a six-membered chelate system. (E = S, Se, Te) as yellow crystalline solid^.['^^ Initial experi- ments show that the new ferrocenyl chalcogenolate ions are suitable ligands for transition metals and rare-earth ele- [*I Priv.-Doz. Dr. F. T. Edelmann, Dipl.-Chem. H. Gornitzka, DipLChem. S. ments. Thus, the ytterbium(iI1) thiolate [{CpFe[C,H,- Besser, Dr. R. Herbst-Inner, Dip1.-Chem. U. Kilimann Institut fur Anorganische Chemie der Universitit (CH,NMe,)S]),Yb] is accessible from 2 and YbC13.[201As a Tammannstrasse 4, D-W-3400 Gottingen (FRG) typical example the reaction of 4 with HgCl, is outlined, [**I This work was supported by the Deutsche Forschungsgemeinschaft. which leads to the mercury@) tellurolate 5. The orange crys-

I260 0 VCH Yerlagsgesellschafr mbH, W-6940 Weinheim. 1992 0570-0833192jO909-1260$3.50+ ,2510 Angew. Chem. Inr. Ed. Engl. 1992, 31 No. 9